masscan
Scan TCP ports with masscan, an asynchronous scanner designed for large network ranges.
About masscan
masscan is an open-source TCP port scanner for large network ranges. It sends SYN packets asynchronously, supports arbitrary port and address ranges in IPv4 and IPv6, and uses parameters and output similar to nmap. It focuses on widespread scanning of many machines rather than in-depth scanning of single machines.
It can also complete TCP connections to grab banners for protocols including HTTP, SSH, FTP, SMTP, Telnet, RDP and others. Because it uses its own TCP/IP stack, scans beyond simple port checks can conflict with the local stack unless run with a separate source IP or with configured source ports and firewall rules.
Key features
- Sends SYN packets asynchronously for large network ranges
- Scans arbitrary IPv4 and IPv6 port and address ranges
- Uses nmap-like parameters and output format
- Grabs TCP banners for HTTP, SSH, FTP and others
- Supports configurable rate and config file via --echo
- Allows separate source IP to avoid stack conflicts
Best for: People who need to scan large IPv4 and IPv6 ranges for open TCP ports.
Good for
- Can scan Internet-scale ranges at 10 million packets per second from a single machine
- Builds with only a C compiler and runs on Linux, Windows, macOS and FreeBSD
- Provides nmap-like usage for users familiar with that scanner
Watch out for
- Own TCP/IP stack can conflict with local stack on scans beyond simple port checks
- Banner grabbing requires a separate IP address or firewall configuration for source ports
- Not intended for in-depth scanning of single machines
masscan at a glance
- Category
- Privacy & Security › Security Tools
- Type
- Open-source project
- Pricing
- Not confirmed. Check the site
- Open source
- Yes · Source code
- Language
- English
- Last checked
- Oct 6, 2026 · Online when checked
- Listed
- Oct 5, 2026
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masscan FAQ
Why does banner grabbing fail or get interrupted?
The local system sends RST packets that end the connection before masscan reads the banner. Use a separate, unused IP address on the local subnet as the source IP.
How do I reuse a scan configuration?
Run with --echo to dump the current configuration to a file, then load it later with -c, for example masscan -c xxx.conf --rate 1000.
What systems can build masscan?
Linux is the primary target. It also builds on Windows with VS10 or MinGW, macOS with Xcode or make, and FreeBSD with gmake.
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